Studies conducted in the Congo Basin forests concluded that soil parameters and large disturbances induced by human activities since 3000–2000 BP could be the main driver for the persistence of long lived ... [more ▼]

Studies conducted in the Congo Basin forests concluded that soil parameters and large disturbances induced by human activities since 3000–2000 BP could be the main driver for the persistence of long lived light-demanding tall tree species. Today most of the timber species belong to this group, among them Pericopsis elata (Fabaceae). Like many other light-demanding trees, this species suffers from important regeneration problems. While the conditions for its establishment must have been met in the past, they obviously have become unfavourable. Because of ongoing logging activities and a natural decline of its populations, this species is recorded in both the IUCN Red List and the CITES Appendix II listings. Our goal was to investigate the roles of both pedological and anthropogenic factors in the persistence of forest patches characterized by this clustered species. Soil surveys, botanical inventories and anthracological excavations were conducted in three different forest sites located in south-eastern Cameroon. P. elata patches (3.3-14.7 ha) were studied and compared to their close surroundings. No statistical differences were observed between the results of botanical inventories conducted inside and outside the patches (Morisita-Horn indices from 0.69-0.77). Soils only differed in Fe content, but otherwise no significant differences could be observed. Charcoal is widespread and abundant in study sites, mostly inside the patches. Charcoal radiocarbon dating (2,150-195 BP) was consistent with decoration techniques of archaeological materials that we discovered. The average age of P. elata individuals coincides with fire events that occurred in a region where fires rarely occur naturally. We present evidence of past anthropogenic disturbances (human settlement, slash-and-burn cultivation) in the Congolese mixed moist semi-evergreen forest in south-eastern Cameroon. We discuss the potential influence of our findings on the management of light-demanding tall trees populations in a context of logging activities. [less ▲]

Top-height growth in even-aged stands of Norway spruce (Piceaabies (L.) Karst.) from Southern Belgium was modelled using functions which provide an algebraic solution for site index (SI) calculation. 16 well known growth model formulations were parameterized using a method which accounts for heterogeneous variance and autocorrelation on a dataset composed of stem analysis data completed by measuring the heights of all the branch whorls to allow for accurate height–age estimates. Comparison of the parameterized models showed that the oblique asymptotic function known as the Duplat and Tran-Ha III model was the most efficient on our dataset. Validation of the selected model on permanent sample plot data showed no evidence of bias over the full range of possible age, height, site index and densities encountered in Norway spruce stands of Southern Belgium. The new height growth model described represents a significant improvement over the previous model of Dagnelie et al. (1988), which was found to be unreliable and required the use of an iterative process to estimate SI. [less ▲]

Soon after death, carcasses release volatile chemicals that attract carrion insects including Silphidae. Nevertheless, it is not known which chemical cues are involved in the attractiveness of the carcass ... [more ▼]

Soon after death, carcasses release volatile chemicals that attract carrion insects including Silphidae. Nevertheless, it is not known which chemical cues are involved in the attractiveness of the carcass. So far, little information is available on the chemical ecology of carrion beetles, particularly concerning the subfamily of Silphinae. The biological role of selected cadaveric volatile organic compounds including: dimethyldisulfide (DMDS), butan-1-ol, n-butanoic acid, indole, phenol, p-cresol, putrescine, and cadaverine on the silphine species, Thanatophilus sinuatus Fabricius, was investigated by using both electrophysiological and behavioural techniques. Among the tested cadaveric compounds, butan-1-ol and DMDS elicited the strongest EAG from both T. sinuatus male and female antennae. In a two-arm olfactometer, males and females were significantly attracted to dimethyldisulfide (DMDS) for both tested doses, whereas only males were attracted to p-cresol at 100 ng. Putrescine was repellent to males at the dose of 1 µg [less ▲]

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), is now considered to be one of the most damaging invasive pests of tomatoes in the world. Tomato is regarded as the main host of T. absoluta ... [more ▼]

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), is now considered to be one of the most damaging invasive pests of tomatoes in the world. Tomato is regarded as the main host of T. absoluta, but the pest can also feed, develop and reproduce on other cultivated Solanaceae, such as potato (Solanum tuberosum L). In the present study, we examined the ability of T. absoluta to develop on four commonly cultivated varieties of potato, under laboratory conditions. The survival rate of T. absoluta did not differ between the five tested host plants (tomato: Solanum lycopersicum cv. Moneymaker; and potato: Solanum tuberosum cv. Spunta, Charlotte, Nicola, and Bintje), but its development time (egg to pupation) was significantly affected. Compared to tomato, development times were longer on Bintje and shorter on Nicola, Charlotte, and Spunta. These results show the high capacity of T. absoluta to develop on potato crops. [less ▲]

To regenerate adventitious shoots from the cotyledon proximal parts of Citrullus lanatus (Thunb.) Matsum. and Nakai ssp. mucosospermus (Fursa) oleaginous type, different concentrations of MS mineral elements, sucrose, 6-benzylaminopurine (BAP) and agar were tested. Shoot induction proved to depend on the interaction between levels of sucrose, BAP and MS mineral elements in the medium. The medium containing 3/2 strength of MS mineral elements, 35 g/l sucrose and 1 mg/l BAP solidified with 6 g/l agar allowed the production of numerous shoots without a callus phase. After 3 weeks of culture, 76.7% of the cotyledon proximal parts induced shoots with an average of 12.26 shoots per explant and a mean shoot length of 17.13 mm. The induced shoots were directly rooted and thus complete plants ready for acclimatization were obtained using a two steps procedure. Depending on the genotype, the shoot induction from cotyledon proximal parts ranged from 54% to 96%. Rooted plantlets were acclimatized and transferred to field, where they grew well, developed flowers and fruits like seeded plants. The assessment of the genetic stability of the in-vitro-regenerated plantlets by means of an Amplified Fragment Length Polymorphism (AFLP) analysis with the combination of 5 primers revealed no differences between regenerated plantlets and mother plants. [less ▲]

Crown rot of banana fruits is caused by a complex of fungal pathogens, the most common of which is Colletotrichum musae, and is one of the main quality defects of exported bananas. Susceptibility of ... [more ▼]

Crown rot of banana fruits is caused by a complex of fungal pathogens, the most common of which is Colletotrichum musae, and is one of the main quality defects of exported bananas. Susceptibility of banana fruits to crown rot is influenced by many pre-harvest factors. The aim of this study was to improve on the methodology for the evaluation of fruit susceptibility and to verify whether cultivation areas in Cameroon as well as seasonal variations have an influence on the susceptibility to crown rot. Fruit susceptibility was evaluated on a monthly basis throughout a year (including the dry and rainy seasons) in three banana plantations located at very different agro-ecological conditions (two in a lowland area and one in a highland area). Fruit susceptibility was determined through an internal necrotic surface (INS) assessment after artificial inoculation with C. musae. The standardization of post-inoculation environmental conditions enabled more reliable INS assessments. Fruit susceptibility was found to be significantly influenced by cultivation area (P<0.001) since fruits grown in low altitude (Dia-dia, Koumba, 80 m) were more susceptible than fruits grown in high altitude (Ekona, 500 m). Although no seasonal effect was observed (P=0.075), there was a highly significant date effect (P<0.001). This was specifically the case in low altitude plantations where fruit susceptibility was higher for some harvest dates within the rainy season. In Ekona, fruit grade and number of leaves on the banana plant were found to be significantly higher than in the two other locations, while black leaf streak disease severity was significantly lower. The potential relationship with fruit susceptibility is fully discussed. [less ▲]

Abstract. The Multicoloured Asian Ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is known to thrive principally in shrubby and arboreal habitats. This study focuses on the occurrence of ... [more ▼]

Abstract. The Multicoloured Asian Ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is known to thrive principally in shrubby and arboreal habitats. This study focuses on the occurrence of this exotic species and its seasonal abundance in various field crops. The abundance of adults, larvae and pupae of H. axyridis was evaluated over a three-year period, from 2009 to 2011, in four important agronomical crops (wheat, corn, broad bean and potato) in Belgium. From May to September, 48 1-m² quadrats were visually inspected in each of the fields sampled on several farms every seven days. H. axyridis colonized and reproduced in all of the four crops studied, with the largest numbers recorded in corn and broad bean crops. Larvae and adults of H. axyridis were recorded mainly in corn and to a much less extent in wheat and potato crops. From 2009 to 2011, the mean weekly abundance of H. ayxridis remained constant except in corn crops, where the recorded densities of all the immature stages and adults were higher in 2011 than in 2009. The population dynamics of aphids and H. axyridis are well described by a symmetric logistic function (S-shape) of cumulative population size. H. axyridis was not always recorded where aphids were abundant, e.g. aphids were abundant on wheat where no H. axyridis were recorded. H. axyridis start reproducing after the peak in aphid population, suggesting that H. axyridis is able to complete its development by feeding on alternative prey such as larvae and pupae of the same and other species of ladybird and other aphidophagous species. H. axyridis is often considered to be bivoltine but it only completes one generation per year in field crops. The second generation generally develops late in the season in other habitats. [less ▲]

in African Journal of Food, Agriculture, Nutrition and Development (2012), 12(7), 7055-7071

The research performed on yam processing mainly concerns the production of crisps and flour. However, its transformation into deep-frozen French fries does not necessitate any other equipment than those ... [more ▼]

The research performed on yam processing mainly concerns the production of crisps and flour. However, its transformation into deep-frozen French fries does not necessitate any other equipment than those used for potatoes. The industrial process of production of frozen French fries traditionally includes a pre-frying step. These steps contribute to the development of color and crispness, and the oil partially absorbed inhibits dehydration during the freezing step. The aim of this study was to optimize frying conditions of deep-frozen fried yam (Dioscorea cayenensis var Kponan) slices. The effect of pre-frying time and temperature, final frying time and temperature on the oil uptake, texture, dry matter and colour of the fried yam slices has been studied. Frying conditions optimized with Box-Behnken experimental design were short pre-frying and frying conditions at high temperature characterized by pre-frying temperature at 157-170°C during 5-9s and frying temperature at 181-188°C for 2min 15s-2min 30s; or long pre-frying and frying conditions at low temperature characterized by pre-frying temperature at 150-158°C during 10-15s and frying temperature 170-177°C for 3-3min 15s. An adiabatic system was also developed by means of an insulator in which the core temperature of fried yam slices can be maintained constant at about 55°C after 15min of cooling, facilitating texture measurements at constant temperature. The present results may help in choosing the yam slices frying condition to be applied in order to achieve the desirable fried yam slices quality, required for protection against certain diseases like obesity. These models may also provide guidance as to how to control these quality parameters by altering four key environmental factors, pre-frying temperature and time and, final frying temperature and time. This process can also be commercialized and does not necessitate any other cost for equipment than those used for potatoes French fries and might be an interesting way of added value processing for this highly perishable yam tuber. [less ▲]

The multicolored Asian ladybeetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) was introduced into Western Europe in the late 1990s. This exotic and invasive species is known to thrive ... [more ▼]

The multicolored Asian ladybeetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) was introduced into Western Europe in the late 1990s. This exotic and invasive species is known to thrive principally in shrubs and arboreal habitats. We focus on a phonological model and on annual abundance in various field crops. The abundance of H. axyridis adults and larvae were evaluated during a three-year period, from 2009 to 2011, in four important agronomical crops (wheat, corn, broad bean and potato) in Belgium. H. axyridis colonizes and reproduces in all four crops studied, with larger densities observed in corn and broad bean. The reproduction of H. axyridis occurs principally in corn and occurred much less in wheat and potato. From 2009 to 2011, abundances of H. axyridis populations were constant except in corn, where the observed densities of all immature stages and adults were higher in 2011 than in 2009. The population dynamics of aphids and H. axyridis were characterized by a symmetric logistic function (S-shape) based on the cumulative population size. [less ▲]

Structure and composition of forest stands are crucial factors for forest planning and biodiversity management. In Belgium, typologies of structure and composition exist to support planning in uneven-aged ... [more ▼]

Structure and composition of forest stands are crucial factors for forest planning and biodiversity management. In Belgium, typologies of structure and composition exist to support planning in uneven-aged broadleaved forests (typically dominated by oak and beech). The principle of these typologies is to classify irregular stands with the percentage of small, medium, large, and very large trees (regarding dbh), and the percentage of basal area of oak and beech. This paper investigates the potential of LiDAR data processed with classification methods (k-nn, K-Means, CART, etc.) to allocate a forest structure and composition type. For this purpose several supervised and unsupervised classification methods are compared, as well as the impact of leaf-on (summer) and leaf-off (winter) data to discriminate the forest types. [less ▲]

The Asian lady beetle Harmonia axyridis Pallas is considered as an invasive species in most territories where it has been introduced. Because aphid honeydew acts as an attractant for many aphid predators ... [more ▼]

The Asian lady beetle Harmonia axyridis Pallas is considered as an invasive species in most territories where it has been introduced. Because aphid honeydew acts as an attractant for many aphid predators and parasitoids, the objectives of this work were to collect and identify the volatile compounds released from the aphid excretory product to evaluate how these semiochemicals could affect the H. axyridis foraging behavior. Twelve volatile chemicals were identified from the Megoura viciae Buckton honeydew including four alcohols, three ketones, three aldehydes, a pyrazine and a monoterpene. The volatiles 3-methyl-1-butanol and 3-methyl-butanal were highlighted as the two most abundant semiochemicals released from the M. viciae honeydew. Vicia faba L. plants treated with crude honeydew attracted more than 80% of the tested individuals with 40% of attracted beetles located on the plant. Four volatile compounds (3-hydroxy-2-butanone, 3-methyl-butanal, 3-methyl-1-butanol and limonene) were also highlighted to attract more than 75% of the coccinellids toward the odor source and to locate about 35% of them on the plants. Limonenewas the most efficient attractant since 89% of the H. axyridis responded to this odor. The use of the identified semiochemicals aswell as the composition of an artificial honeydew could certainly be helpful to control the dispersal of the Asian lady beetle H. axyridis. [less ▲]

The role of earthworms in soil fertility and transformation of organic waste was regulary cited to be of first importance. Associated to these macro-invertebrates, a large diversity of micro-orgnisms are ... [more ▼]

The role of earthworms in soil fertility and transformation of organic waste was regulary cited to be of first importance. Associated to these macro-invertebrates, a large diversity of micro-orgnisms are found indirectly in their closed environment or directly in their gut. Functional aspects of these interactions and symbiosis in relation with soil characteristics and fertility rates are poorly developed. Here, the micro-organisms diversity and potential related functions of earthworm gut were investigated using a proteiomic approach for both protein and micro-organism identifications. Microbial community investigation was detected by proteomic approach based on bidimensional electrophoresis coupled with mass spectrometry using Matrix Assisted Laser Desorption Ionisation – time of flight (Maldi-Tof). Diversity of gut associated bacterial communities was discussed. Indeed, application of particular crop production practices such as crop residue management at the field level could regulate the gut bacterial communities in earthworm but also microbials in soils. Agricultural systems had to consider the microbial and associated organisms in the soil to enhance fertlility and crop production in sustainable ways. [less ▲]

Earthworms are largely distributed in terrestrial ecosystems and their abundance and diversity in soils are significantly affected by biotic (macro- and micro-organisms) and abiotic factors: soil ... [more ▼]

Earthworms are largely distributed in terrestrial ecosystems and their abundance and diversity in soils are significantly affected by biotic (macro- and micro-organisms) and abiotic factors: soil properties (pH, texture, structure…); agricultural management system and climate change. Here, tillage effect of earthworm population combined with crops residual management was investigated and correlated with soils properties. From wheat experimental field plots, the diversity of earthworm according to the field crop management was assessed. Application of particular crop production practices such as the integration of different levels of crop residues, diverse parts of wheat straws, at the field level regulate earthworm diversity and population abundance. Indeed, tillage reduced earthworm population with a 35% rate also corresponding to changes in soil properties. Agricultural practices had to be adapted to include consideration on macro-invertebrate abundance and diversity to maintain efficient soil fertility and allow sustainable crop production [less ▲]

Cananga odorata (Lam.) Hook.f. Thomson forma genuina (Annonaceae) is a tropical tree, grown for the production of ylang-ylang essential oil, which is extracted from its fresh and mature flowers. Despite ... [more ▼]

Cananga odorata (Lam.) Hook.f. Thomson forma genuina (Annonaceae) is a tropical tree, grown for the production of ylang-ylang essential oil, which is extracted from its fresh and mature flowers. Despite its economic and social importance, very little information is available on its variability and the possible factors causing it. Therefore, the relationship between the genetic structure, revealed by amplified fragment length polymorphism (AFLP), and the essential oil chemical composition, determined by GC/MS analysis, of ylang-ylang grown in semi-managed systems in three Indian Ocean islands (Grande Comore, Mayotte, and Madagascar) was investigated. Our results revealed a low genetic variation within plantations and contrasted situations between islands. Variations of the chemical composition could be observed within plantations and between islands. The genetic differentiation pattern did not match the observed pattern of chemical variability. Hence, the chemical variation could not be attributed to a genetic control. As Grande Comore, Madagascar, and Mayotte present different environmental and agronomic conditions, it can be concluded that the influence of these conditions on the ylang-ylang essential oil composition is consistent with the patterns observed. Finally, several strategies were proposed to valorize the chemical composition variations. [less ▲]